Measurement of the shape or the state of a surface of an object is carried out for an instrumentation of the object's characters, a decision whether the quality of the object is good or not as a product, and the like. In particular, measurement of the shape or the state of the surface of the object is often used for measuring the irregularity of a surface of an object having an approximate plate-like shape.
FIG. 9 shows a typical example of a measuring apparatus for measuring the irregularity of the surface of the object having an approximate plate-like shape. As shown in FIG. 9, the measuring apparatus is provided with (a) a light source 910 for generating substantially parallel light beams, (b) a half mirror 920 for accepting the light beams output from the light source 910 and for outputting these light beams toward a specific measurement objective region on the object 990 to be measured, (c) an optical image formation system 930 for receiving the reflected light from the measurement objective region of the object 990 to be measured and for forming an optical image thereof, (d) an image pickup part 940 having a light receiving surface 941 at the image formation surface of the optical image formation system 930, and (e) an image information processor 950 for collecting the luminance data output from the image pickup part 940 and for image processing the collected data.
By using the above-described measuring apparatus, measurement of the shape or the like of the measurement objective region is carried out as follows. A substantially parallel light beam outputs from the light source 910 are irradiated through the half mirror 920 onto measurement objective regions of the object 990 to be measured. Light beams reflected from the measurement objective region forms an image through the image formation system 930, and the formed image is picked up by the image pickup part 940. The picked up image results are output from the image pickup part 940 and are collected by the image information processor 950. The processor 950 reconstructs the image of the measurement objective region by processing the collected luminance data. By inspection of the obtained image of the measured objective region, the presence or absence of irregularity or the position of the irregularity is measured through fading or blurry portions in the image.
Conventionally, since an object shape measurement has been carried out as described above, an approximate shape of the irregular portion could be recognized. However, when the irregularity is formed as a periodic pattern, for example, a circuit pattern is formed on a surface of a wafer, a precise measurement for the shape of the irregular pattern could not be performed.
Accordingly, in order to precisely measure the shape of the irregular pattern, use of a large scale, complicated and expensive apparatus such as a scanning confocal electron microscope has been required.
The present invention was developed in view of the above-described problems. An object of the present invention is to provide an improved surface inspecting method which enables measurement of the configuration of a pattern with irregularity in a wide surface region with a high accuracy and in a single operation by using an apparatus having relatively simple construction. Another object of the present invention is to provide an improved surface inspecting apparatus having a simple construction for suitably carrying out the surface inspecting method according to the invention.